Eighteen wheelers, and smaller trucks as well such as milk trucks and armored cars, almost universally use a standard ten-lug wheel configuration. The hubs of these wheels must be removed every time the brakes are accessed for service. The hub mounts to the axle, with the brake drum being bolted to the inside of the hub and extending up over the brake shoes. The hub and drum must bear the weight of the truck as well as the braking force exerted on the drums by the shoes. This structure has to be very strong and is quite heavy. The weight of the hub, coupled with the weight and awkward bell shape of the drum, makes it difficult for service people to remove the drum for servicing the brake.
Currently, a wheel dolly can be used to remove the dual wheels, hub and drum as a single unit. If no wheel dolly is available, a fork lift or pallet jack can be used in the same way. Removal using these lifting devices works very well, and when replacing bearings or seals, jobs not requiring separation of the hubs from the wheels, the same equipment can be used to remount the wheels, hub and drum as a single unit, with no problem.
However, when replacing wheel studs or servicing the brake drum, the wheels have to be removed from the hub. Once removed, it is very difficult to re-assemble the components when the hub is not mounted on the truck because of the bulk and weight of the wheels as well as the other parts. Therefore, the wheel dolly is useless. The hub and drum must be mounted first, and the wheel dolly is not designed for that. Manually mounting the hub and drum involves considerable effort and some risk of injury. In addition to the weight, there are no adequate handhold positions on the drum, and the location of the center of gravity is a foot or more away from the person(s) trying to mount the assembly.
When trying to lift the hub/drum at an awkward angle with a displaced center of gravity, it is quite heavy. But the actual weight is not so great that two people could not carry it easily with a proper horizontal spanner bar which eliminates all but gravitational forces on the load, eliminating the need to exert muscular force at awkward and ineffective angles just to maintain the orientation of the load. A carrier using this "pole principle" of native bearers can be used to facilitate handling these large hubs, converting a difficult and dangerous job to a simple one with little risk of injury.
The pole principle works with two men, but one man cannot hold both ends of the pole. It would be convenient at times to be able to connect and suspend the hub from a "Cherry Picker," the mobile frame that is used to move engines from engine compartments, so that a man working alone could maneuver it. The pole concept is adapted to cherry pickers inasmuch as the suspension and lifting force comes from the top. Virtually every shop has a cherry picker, which is useful in doing such a variety of chores around the shop that its utility far outweighs its storage burden.